Models with \(X \sim 10^{15}\)  and a few orders of magnitude above this are consistent with all current constraints on PBH dark matter[1]}. For those in the range \(10^{6} < X <10^{15}\)  we must solve the complicated problem of black hole merger and coalescence during a PBH matter dominated era, in order to determine whether signals from black hole decay can be used to rule these models out. Furthermore, these models could be models of decaying dark matter, some of which have been invoked to resolve the Hubble tension and other problems of vanilla LCDM models[2]}. The possibility of several species of black holes with masses spanning the range \(10^{12} - 10^{21}\)  in Planck units would lead to models of partially decaying dark matter, with considerable flexibility in fitting cosmological observations.
